DETECTING AND PURGING COMBUSTIBLE GASES FROM HRSG CAVITIES

摘要

A gas turbine (10) combined cycle system with a heat recovery steam generator (12) which may include enclosed adjacent cavities (30) may accumulate combustible gas mixtures during shut-downs. Gas detectors (38, 46, 48) located in the heat transfer section (30) of the heat recovery steam generator (12), in related duct work (16) and in the adjacent cavities (30) detect the presence of these gas mixtures and produce appropriate signals. A signal from the detectors (38, 46, 48) in the cavities (30) initiate the aspiration (42) of the mixture from the cavity (30). Signals from the detectors (38, 46, 48) in the heat transfer section and ducts as well as from the cavities (30) control the gas turbine (50) so that upon start-up, no fuel is introduced to the gas turbine (10) so that the gas turbine (10) forces purge air through the heat recovery steam generator (12). When all of the signals indicate that no combustible gas mixtures are present, the gas turbine (10) is ignited.